Non-contacting actuator for rocker arm assembly latches

Abstract

An internal combustion engine includes a valvetrain having a rocker arm assembly including a rocker arm on which a latch pin is mounted. An actuator for the latch pin, including an electromagnet, is mounted separately from the rocker arm. Therefore, the rocker arm is able to move independently from the electromagnet. The electromagnet is operative to cause the latch pin to actuate through magnetic flux following a magnetic circuit that passes through the rocker arm. Mounting the electromagnet apart from the rocker arm allows wires powering the electromagnet to be held in relatively static positions. The magnetic circuit is arranged to bring magnetic flux into the latch pin, or a co-acting part, within the volume of the rocker arm. This enables a compact design that is suitable for installation in engines where the available space under the valve cover may be very limited.

The invention claimed is: 
     
       1. A valvetrain for an internal combustion engine of a type that has a combustion chamber, a moveable valve having a seat formed in the combustion chamber, and a camshaft, comprising:
 a rocker arm assembly comprising a rocker arm and a cam follower configured to engage a cam mounted on a camshaft as the camshaft rotates; and 
 a latch assembly comprising a latch pin that is mounted on the rocker arm and an actuator comprising an electromagnet that is mounted to a component of the engine other than the rocker arm; 
 wherein the latch pin is moveable between first and second positions; 
 the rocker arm is moveable independently from the electromagnet; 
 the actuator and the rocker arm assembly are positioned to make the electromagnet operable to cause the latch pin to translate between the first position and the second position; and 
 the actuator and the rocker arm assembly are positioned to make the electromagnet operable to cause the latch pin to translate between the first position and the second position through magnetic flux that passes through the rocker arm. 
 
     
     
       2. A valvetrain according to  claim 1 , further comprising:
 a pivot providing a fulcrum for the rocker arm; 
 wherein the electromagnet is mounted to the pivot. 
 
     
     
       3. An internal combustion engine comprising a valvetrain according to  claim 1 , wherein the component of the engine to which the electromagnet is mounted is in a fixed position relative to the combustion chamber. 
     
     
       4. A valvetrain according to  claim 1 , wherein:
 the rocker arm has a load-bearing structure; and 
 the magnetic flux passes through that load-bearing structure. 
 
     
     
       5. A valvetrain according to  claim 1 , wherein:
 the rocker arm has a load-bearing structure that is paramagnetic; and 
 the magnetic flux passes through a pole piece fixed to that load-bearing structure. 
 
     
     
       6. A valvetrain according to  claim 1 , wherein the rocker arm is formed primarily of low coercivity ferromagnetic material. 
     
     
       7. A valvetrain according to  claim 1 , further comprising:
 a pivot providing a fulcrum for the rocker arm; 
 wherein the pivot, the actuator, and the rocker arm assembly are structured and positioned to make the electromagnet operable to cause the latch pin to translate between the first position and the second position through magnetic flux that passes through both the pivot and the rocker arm. 
 
     
     
       8. A valvetrain according to  claim 1 , wherein:
 the magnetic flux considered in one of a North to South or South to North direction enters the latch pin directly from, or across only an air gap from, the rocker arm and leaves the latch pin crossing directly from or across only an air gap from the latch pin to a pole piece of the actuator; and 
 the rocker arm is moveable independently from the pole piece of the actuator. 
 
     
     
       9. A valvetrain according to  claim 1 , wherein the latch pin completes a magnetic circuit that makes the electromagnet operative to cause the latch pin to translate between the first position and the second position such that if the latch were replaced by one made entirely from aluminum, the electromagnet would not be so operative. 
     
     
       10. A valvetrain according to  claim 1 , wherein:
 one of the first and second latch pin positions provides a configuration in which the rocker arm assembly is operative to actuate the moveable valve in response to rotation of the camshaft to produce a first valve lift profile; and 
 the other of the first and second latch pin positions provides a configuration in which the rocker arm assembly is operative to actuate the moveable valve in response to rotation of the camshaft to produce a second valve lift profile, which is distinct from the first valve lift profile, or the moveable valve is deactivated. 
 
     
     
       11. A valvetrain according to  claim 1 , wherein:
 the rocker arm assembly is operative to form a force transmission pathway between the cam and the moveable valve; and 
 the force transmission pathway includes the rocker arm. 
 
     
     
       12. An internal combustion engine comprising:
 a valvetrain according to  claim 1 ; 
 a cylinder head comprising a combustion chamber; and 
 a valve cover; 
 wherein parts of the internal combustion engine including the cylinder head and the valve cover enclose a space between the cylinder head and the valve cover; 
 one of the parts that encloses the space is closer to the latch pin than any of the other parts enclosing the space; 
 there is a shortest path between the latch pin and the closest of the plurality of parts; 
 a pole piece of the actuator is positioned along the shortest path. 
 
     
     
       13. An internal combustion engine according to  claim 12 , wherein parts of the engine along the shortest path consist essentially of the pole piece of the actuator. 
     
     
       14. A valvetrain according to  claim 1 , wherein when the rocker arm is not being lifted by any cam, a line passing through the latch pin and oriented in a direction along which the latch pin translates between its first and second positions does not pass through the electromagnet. 
     
     
       15. A valvetrain according to  claim 1 , further comprising:
 a second rocker arm assembly comprising a second rocker arm and a second latch assembly comprising a second latch pin mounted to the second rocker arm and moveable between first and second positions; 
 wherein the electromagnet is also operable to cause the second latch pin to translate between its first and second positions. 
 
     
     
       16. A valvetrain according to  claim 1 , wherein:
 the latch assembly is structured to stabilize the latch pin in the first position against perturbations toward the second position independently from the electromagnet; and 
 the latch assembly is structured to stabilize the latch pin in the second position against perturbations toward the first position independently from the electromagnet. 
 
     
     
       17. A valvetrain according to  claim 16 , wherein:
 the latch assembly further comprises a permanent magnet in a position such that: 
 with the latch pin in the first position, and absent any magnetic fields generated by the electromagnet, the permanent magnet is operative to stabilize the latch pin in the first position through magnetic flux following a first magnetic circuit; and 
 with the latch pin in the second position, and absent any magnetic fields generated by the electromagnet, the permanent magnet is operative to stabilize the latch pin in the second position through magnetic flux following a second magnetic circuit that is distinct from the first magnetic circuit. 
 
     
     
       18. A valvetrain according to  claim 17 , wherein one of the first magnetic circuit and the second magnetic circuit passes through the actuator and the other does not. 
     
     
       19. A valvetrain according to  claim 17 , wherein the permanent magnet is rigidly mounted in a fixed position on the rocker arm. 
     
     
       20. A valvetrain according to  claim 17 , wherein the permanent magnet is mounted to the actuator. 
     
     
       21. A valvetrain according to  claim 1 , wherein the latch pin passes through a hydraulic chamber formed by the rocker arm. 
     
     
       22. A method of manufacturing a valvetrain according to  claim 1 , comprising:
 manufacturing a rocker arm with a hydraulic chamber for receiving a hydraulically actuated latch pin; and 
 forming a valvetrain according to  claim 1  using the manufactured rocker arm as the rocker arm of  claim 1  and installing the latch pin of  claim 1  through the hydraulic chamber. 
 
     
     
       23. A valvetrain for an internal combustion engine of a type that has a combustion chamber, a moveable valve having a seat formed in the combustion chamber, and a camshaft, comprising:
 a rocker arm assembly comprising a rocker arm and a cam follower configured to engage a cam mounted on a camshaft as the camshaft rotates; and 
 a latch assembly comprising a latch pin that is mounted on the rocker arm and an actuator comprising an electromagnet that is mounted to a component of the engine other than the rocker arm; 
 wherein the latch pin is moveable between first and second positions; 
 the rocker arm is moveable independently from the electromagnet; 
 the actuator and the rocker arm assembly are positioned to make the electromagnet operable to cause the latch pin to translate between the first position and the second position; and 
 the rocker arm has a load-bearing structure that completes a magnetic circuit that makes the electromagnet operative to cause the latch pin to translate between the first position and the second position such that if the rocker arm were replaced by one made entirely from aluminum, the electromagnet would not be so operative. 
 
     
     
       24. A valvetrain for an internal combustion engine of a type that has a combustion chamber, a moveable valve having a seat formed in the combustion chamber, and a camshaft, comprising:
 a rocker arm assembly comprising a rocker arm and a cam follower configured to engage a cam mounted on a camshaft as the camshaft rotates; and 
 a latch assembly comprising a latch pin that is mounted on the rocker arm and an actuator comprising an electromagnet that is mounted to a component of the engine other than the rocker arm; 
 wherein the latch pin is moveable between first and second positions; 
 the rocker arm is moveable independently from the electromagnet; 
 the actuator and the rocker arm assembly are positioned to make the electromagnet operable to cause the latch pin to translate between the first position and the second position; and 
 the electromagnet is mounted in a position such that while the cam is on base circle a line that passes through the latch pin and is oriented in a direction along which the latch pin translates between its first and second positions does not pass through the electromagnet. 
 
     
     
       25. A valvetrain according to  claim 24 , wherein the electromagnet is mounted in a position such that any line that is oriented in a direction along which the latch pin translates between its first and second positions and that passes through the latch pin while the cam is on base circle does not pass through the electromagnet. 
     
     
       26. A valvetrain according to  claim 24 , wherein:
 the electromagnet is mounted in a position such that any line that is oriented in a direction along which the latch pin translates between its first and second positions and that passes through the latch pin does not pass through the electromagnet; and 
 the positioning of the electromagnet is such that the foregoing condition regarding the electromagnets positioning remains satisfied even as the latch pin goes through a range of motion in conjunction with the rocker arm under the influence of the cam. 
 
     
     
       27. A valvetrain according to  claim 24 , wherein one of the rocker arm and a pivot that provides a fulcrum for the rocker arm assembly completes a magnetic circuit that makes the electromagnet operative to cause the latch pin to translate between the first position and the second position through magnetic flux. 
     
     
       28. An internal combustion engine comprising a valvetrain according to  claim 24 , wherein the electromagnet is held in a fixed position relative to the combustion chamber. 
     
     
       29. A valvetrain for an internal combustion engine of a type that has a combustion chamber, a moveable valve having a seat formed in the combustion chamber, and a camshaft, comprising:
 a rocker arm assembly comprising a rocker arm and a cam follower configured to engage a cam mounted on a camshaft as the camshaft rotates; and 
 a latch assembly comprising a latch pin that is mounted on the rocker arm and an actuator comprising an electromagnet that is mounted to a component of the engine other than the rocker arm; 
 wherein the latch pin is moveable between first and second positions; 
 the rocker arm is moveable independently from the electromagnet; 
 the actuator and the rocker arm assembly are positioned to make the electromagnet operable to cause the latch pin to translate between the first position and the second position; 
 the valvetrain further comprises a pivot that provides a fulcrum for the rocker arm; and 
 the actuator and the fulcrum are positioned to make the electromagnet operable to cause the latch pin to translate between the first position and the second position through magnetic flux that passes through the pivot. 
 
     
     
       30. A valvetrain for an internal combustion engine of a type that has a combustion chamber, a moveable valve having a seat formed in the combustion chamber, and a camshaft, comprising:
 a rocker arm assembly comprising a rocker arm and a cam follower configured to engage a cam mounted on a camshaft as the camshaft rotates; and 
 a latch assembly comprising a latch pin that is mounted on the rocker arm and an actuator comprising an electromagnet that is mounted to a component of the engine other than the rocker arm; 
 wherein the latch pin is moveable between first and second positions; 
 the rocker arm is moveable independently from the electromagnet; 
 the actuator and the rocker arm assembly are positioned to make the electromagnet operable to cause the latch pin to translate between the first position and the second position; 
 the valvetrain further comprises a pivot that provides a fulcrum for the rocker arm; and 
 the actuator and the fulcrum are positioned to make the electromagnet operable to cause the latch pin to translate between the first position and the second position through magnetic flux following a magnetic circuit that includes a part of the pivot that if replaced by a part made from aluminum would render the electromagnet no longer so operative. 
 
     
     
       31. A valvetrain for an internal combustion engine of a type that has a combustion chamber, a moveable valve having a seat formed in the combustion chamber, and a camshaft, comprising:
 a rocker arm assembly comprising a rocker arm and a cam follower configured to engage a cam mounted on a camshaft as the camshaft rotates; and 
 a latch assembly comprising a latch pin that is mounted on the rocker arm and an actuator comprising an electromagnet that is mounted to a component of the engine other than the rocker arm; 
 wherein the latch pin is moveable between first and second positions; 
 the rocker arm is moveable independently from the electromagnet; 
 the actuator and the rocker arm assembly are positioned to make the electromagnet operable to cause the latch pin to translate between the first position and the second position; 
 the electromagnet is operable to cause the latch pin to translate between the first position and the second position through magnetic flux that follows a magnetic circuit; and 
 the magnetic circuit passes from the electromagnet to a pole piece that has a fixed location on the rocker arm, from the pole piece to the latch pin, from the latch pin across an air gap, and from across the air gap back to the electromagnet. 
 
     
     
       32. A valvetrain according to  claim 31 , further comprising:
 a second pole piece, which is mounted to a component of the engine that is distinct from the rocker arm; 
 wherein the magnetic circuit passes from the electromagnet to the second pole, from the second pole piece to the first pole piece, and from the first pole piece to the latch pin.